Explanation

(d) According to the equilibrium theorem, the molar heat capacities should be independent of temperature. However, variations in $C_{V}$ and $C_{P}$ are observed as the temperature changes. At very high temperatures, vibrations are also important and that affects the values of $C_{V}$ and $C_{P}$ for diatomic and polyatomic gases. Here in this question according to given information (d) may be correct answer